Heretofore there have been many different types of retroreflective laminates provided and used widely for a number of industrial and commercial purposes including highway signs, traffic markers, etc., wherein the signs or markers have the characteristic of reflecting a major portion of the light rays striking the sign regardless of the angle of incidence of such light rays and wherein the reflected light rays return to the light source substantially along the initial light ray path.
There has been a great amount of patent and commercial activity on various procedures to make laminates and the compositions thereof in the retroreflective laminate field. Typical prior patents include U.S. Pat. Nos. 2,432,928; 2,440,584; 2,543,800; 2,397,702 and 2,354,049 on various types of retroreflective laminates, including a layer of glass beads therein, and their methods of production as have been developed heretofore.
In the use of these retroreflective laminates, it is very important that the laminates have very good optical clarity, that it have an efficient reflective action for light rays striking the laminate at a relatively low angle of incidence, the laminates preferably are flexible, they should be adapted to have printed matter and inks deposited therein, the various layers in the laminates must be bonded together tightly, the laminate must be weather resistant, the beads must be securely positioned in the laminate, etc.
Some problems that have existed heretofore in the production of some retroreflective laminates is that a relatively high percentage of scrap has resulted in many instances by prior methods of manufacture of retroreflective laminates, the laminates in some instances have not been of uniform physical size, thickness and properties, and/or the beads may not be securely positioned in the laminate.
While many different types of laminates have been proposed and provided heretofore in the retroreflective laminate field, there is a need for a retroreflective laminate having a uniform physical and light reflecting characteristics over the entire area of the laminate, and to provide a laminate having a long service life and adapted to withstand continued exposure to the weather. Improved procedures for making the laminates also could be used in the industry.
It is the general object of the present invention to provide a retroreflective laminate having uniform physical properties throughout, which laminate has excellent resistance to weathering and has good bonding between all layers in the laminate, and to provide a method of producing an improved retroreflective laminate in which the glass beads are securely positioned.
Another object of the invention is to provide a laminate having a face or surface layer formed from a partially cured resilient acrylic material which is quite resistant to degradation and provides a long service life in a retroreflective laminate exposed to the weather, which face surface has excellent optical properties, is resistant to solvents, resistant to atmospheric degradation and can accept printing data and inks thereon.
Another object of the invention is to utilize improved bonding techniques for securing a layer of glass beads in a retroreflective laminate and for forming and using a preformed reflective backing or spacer layer in the laminate which layer is positioned in close, accurately spaced uniform relation to the glass beads in the laminate product.
Other objects of the invention relate to the provision of a chrome complex release coat on a carrier film used in producing the laminate of the invention and which has the acrylic polymer film material received and processed thereupon; to use the same basic polyvinyl butyral material in forming a binder layer, a spacer layer and a secondary binder or a sealer layer in the laminate; to improve the bonding of the layer of glass beads in the laminate by a liquid sealer layer applied to the exposed surfaces of the glass beads and binder layer and dried thereon prior to association of the preformed reflective or spacer layer thereto; to provide a nitrocellulose bonding layer for securely attaching the glass bead binder layer to the acrylic face layer in the laminate; to preform a spacer layer for use in the laminate and apply a metallized backing layer thereto prior to laminating the spacer layer with a second preformed laminate having a layer of glass beads thereon and exposed on one surface thereof for engagement with the spacer layer; and to control the lamination action and obtain uniform contact in adjacent layers when forming the end product by control of the durometer of a rubber backing roll used in the laminating action.
The foregoing and other objects of the invention will be apparent from the following specification.
It should be noted that the various layers in the laminate of the invention are shown in the drawings of exaggerated thickness and that all of such layers are quite thin such as from about 1/2 up to about 4 or 5 mils in thickness as indicated in the specification.